Apparatus for manufacturing single crystal

ABSTRACT

This invention provides a method and a apparatus capable of manufacturing single crystals with an oxygen density of less than 12×10 17  atoms/cm 3  or less than 10×10 17  atoms/cm 3 , and wherein the oxygen density of the single crystal produced is uniformly distributed along its longitudinal axis. The electrical power inputted into the main heater 6 surrounding the quartz crucible 4 and the top heater 9 shaped like a reverse frustrated cone and disposed above the quartz crucible 4, is controlled to keep the temperature of the melt 5 in a preset range during the process of pulling up the single crystal silicon 10. When combining the main heater 6 and the top heater 9, the heat emitted from the main heater 6 can be kept small, and the heat load on the quartz crucible 4 and the amount of oxygen released from the quartz crucible 4 and dissloved into melt 5 can be reduced. Therefore, a single crystal of low oxygen density and with uniformly distributed oxygen density along its longitudinal axis can be obtained. Furthermore, the single-crystal silicon 10 can be assigned a proper thermal history. In the above process, if a magnetic field is applied to the melt, then single crystals of much lower oxygen density can be obtained.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing singlecrystals by the Czochralski Method (CZ method), particularly to a methodand a apparatus for manufacturing single crystals which can reduce theoxygen density along longitudinal axes of produced single crystals.

2. Description of the Prior Art

Single crystals are conventionally produced by the CZ method. In the CZmethod, polycrystalline silicon lumps are fed into a quartz crucible ofa single crystal manufacturing apparatus, then the quartz crucible isheated by heaters disposed therearound to melt the polycrystallinesilicon lumps, thereafter a seed crystal installed on a seed chuck isdipped into the melt. After that, the seed chuck and the quartz crucibleare respectively driven to rotate in opposite or identical directions,and at the same time the seed chuck is pulled up to grow asingle-crystal silicon ingot of predetermined diameter and length.

Due to the fact that the inner surface of the crucible is in contactwith the melt, oxygen contained in the inner surface of the crucibledissolves into the melt. Most of the oxygen evaporates through thesurface of the melt and is expelled out of the single crystalmanufacturing apparatus, however, the remaining oxygen enters the singlecrystal being pulled up. The density of oxygen in single crystals ishigh at the beginning of the pulling up operation and declines followingan increase of the solidification ratio. The oxygen entering the singlecrystal plays the role of cleaning up contamination by a very smallamount of heavy metal during the manufacturing process of semiconductordevices, in other words, if exhibits an intrinsic-gettering effect.However, when oxygen remains in the active layers of wafer surfaces, itbecomes nuclei of oxidation-induced stacking faults and thus negativelyaffects the electric characteristics of semiconductor devices.

To equalize oxygen density along the longitudinal axis of asingle-crystal ingot, various proposals are recommended. For example, amethod for manufacturing single crystals is disclosed in the Japanesepublication gazette TOKU KAIHEI 2-192486, in which the output of heatersdisposed around the body and the bottom of a quartz crucible iscontrolled. Also, a method for manufacturing single crystals isdisclosed in TOKU KAIHEI 2-217388, in which a quartz crucible isprovided with heat shield members used for covering all of the quartzcrucible except for the single-crystal silicon pulling up zone, duringthe operation of pulling up single-crystal silicon by the CZ method, andthe output of heaters disposed around the body and the bottom of thequartz crucible are controlled. Furthermore, in TOKU KAIHEI 2-229786, ahorizontal magnetic field is applied to the melt in a quartz crucibleand the output of heaters disposed around the body and the bottom of thequartz crucible is controlled.

Also, in TOKU KAI HEI 5-294782, the oxygen density of single-crystalsilicon is reduced by controlling the melt temperature via a main heaterand a multiple staged sub-heater disposed above the melt and shaped inconcentric circles.

However, in recent years, as the volume of quartz crucibles risesfollowing the enlargement of the sizes of single crystal silicon ingots,both an electric amount of power required by heaters and surface ofquartz crucibles in contact with melt are increased, and then the amountof oxygen coming from quartz crucibles and dissolved in melt has alsoincreased. Hence, it is difficult to obtain low oxygen single crystalswith oxygen density of less than 12×10¹⁷ atoms/cm³ or extreme low oxygensingle crystals with oxygen density of less than 10×10¹⁷ atoms/cm³ byusing above conventional methods. In addition, it takes a long time togrow large single-crystal silicon, therefore there exists a danger ofworsening quality of quartz crucibles by heat load and polycrystallizingsingle crystals during the pulling up operation. In view of the abovesituation, it is difficult to impose minimum heat load on quartzcrucibles during pulling up operation as conventionally. Furthermore, inTOKU KAI HEI 6-183876, the inventors of this invention disclosed amethod and an apparatus suitable for recharging material whensingle-crystal silicon has been pulled up, or for applying asupplementary charge of material when a preset amount of material hasbeen melted and additional material is required to increase the amountof melt.

SUMMARY OF THE INVENTION

In view of the above described defects, the object of the presentinvention is to provide a method and an apparatus capable ofmanufacturing a single-crystal silicon of large diameter, the oxygendensity of which is uniformly distributed along its longitudinal axisand has a value of less than 12×10¹⁷ atoms/cm³ or less than 10×10¹⁷atoms/cm³.

To achieve the above object, according to this invention, an apparatusfor manufacturing single-crystal silicon by the CZ method ischaracterized in that a top heater is disposed above the quartz crucibleand the top heater is provided with at least one of the followingfunctions:

(1) rectifying carrier gases;

(2) heating the raw material and a melt of the raw material fed into thequartz crucible;

(3) heating the single crystal silicon being pulled up;

(4) depressing the amount of oxygen dissolved into the melt from thequartz crucible and the deterioration of the quartz crucible induced byheat load; and

(5) giving thermal history to the single-crystal silicon pulled up fromthe melt.

According to the above structure, a top heater combined with arectifying cylinder for the purpose of rectifying carrier gases isdisposed above the quartz crucible, therefore the amount of heat emittedfrom the main heater can be minimized if the top heater and the mainheater are used simultaneously. As a result, the heat load on the quartzcrucible and the amount of oxygen dissolved into the melt from thequartz crucible can be reduced. Furthermore, the single-crystal siliconis heated by the top heater when passing a preset temperature zone, thusslip back can be prevented and a preset thermal history can be given tothe single-crystal silicon.

The top heater in the apparatus for manufacturing single crystal siliconaccording to this invention is a reverse-frustrated cone opened at itstwo ends or a heater provided with one- or multiple-stage cylinders.

By this arrangement, the single-crystal silicon can be heated to apredetermined temperature when passing through the top heater and thuscan be given a proper thermal history. When a multiple-stage heater isused, the heated status can be far more precisely controlled rather thanwith a one stage heater.

Furthermore, in the top heater according to this invention, at least thesurface facing the melt is covered by reflection plates.

By using the reflection plates, radiation heat coming from the mainheater, the quartz crucible, and the melt is reflected back on the melt,therefore electrical power required by the main heater can be furtherreduced.

Furthermore, in the apparatus for manufacturing single crystal siliconaccording to this invention, the top heater is disposed adjacent to thelower end of the cylindrical or reverse-frustrated cone-shapedrectifying cylinder

By this arrangement, the top heater is disposed near the melt surface,to facilitate the heating of melt or polycrystalline silicon lumps andkeep warm the single crystal silicon being pulled up.

In the apparatus for manufacturing single-crystal silicon according tothis invention, means for applying a magnetic field is provided.

By applying a horizontal magnetic field or cusp magnetic field to thequartz crucible and melt, convection of melt can be prevented. Thus, theamount of oxygen dissolved in the melt is reduced and the oxygen densityin the single crystal silicones also decreases.

The method for manufacturing single-crystal silicon according to thisinvention is characterized in that the electrical power inputted intothe main heater surrounding the quartz crucible and the top heaterdisposed above the quartz crucible is controlled to keep the temperatureof melt within a predetermined range when pulling up the single-crystalsilicon.

According to the above structure, the melt is heated by the top heater,even if the output of the main heater is reduced, the temperature ofmelt can also be kept within a predetermined range. Therefore, the heatload on the quartz crucible decreases, deterioration of the quartzcrucible can be prevented, and the ratio of single crystallization canbe enhanced. Furthermore, the single-crystal silicon pulled up from meltis heated by the top heater, the cooling temperature gradient is small,especially, when passing through the temperature zone of from 1150° C.to 1080° C., thus, the number of small crystal defects can thus bereduced.

Also, the method for manufacturing single-crystal silicon according tothis invention is characterized in that a magnetic field is applied tothe melt and the electrical power inputted into the main heatersurrounding the quartz crucible and the top heater disposed above thequartz crucible is controlled when pulling up the single-crystalsilicon.

By this arrangement, melt is heated by the main heater and the topheater, the heat load on the quartz crucible is reduced from that whenonly using a main heater or using a main heater and a bottom heater incombination, and the amount of oxygen in the melt also decreases. Inaddition, a horizontal magnetic field or a cusp magnetic field isapplied to the melt, thus convection along the internal surface of thequartz crucible is prevented and the amount of oxygen dissolved in themelt is further reduced. Therefore, single-crystal silicon with anexceptionally low oxygen density can be obtained.

In addition, the method for manufacturing single-crystal siliconaccording to this invention is characterized in that the electricalpower inputted into the main heater surrounding the quartz crucible andthe top heater disposed above the quartz crucible is controlled to meltpolycrystalline silicon lumps, and a predetermined amount ofsupplementary melt is fed thereinto.

If the top heater is used, the recharge material or supplementary chargecan be melted easily. Furthermore, the output of the main heater can bereduced, thus heat load of the quartz crucible decreases anddeterioration of the quartz crucible can be prevented. Consequently, inthe operation of pulling up the single-crystal silicon, even if the samequartz crucible is repeatedly used for several times the ratio of singlecrystallization will not decline.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more fully understood by reading thesubsequent detailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a schematic vertical cross-sectional view of the firstembodiment of the apparatus for manufacturing single-crystal siliconaccording to this invention;

FIG. 2 is a side view showing the shape and structure of a first exampleof the top heat;

FIG. 3 is a side view showing the shape and structure of a secondexample of the top heat;

FIG. 4 is a side view showing the shape and structure of a third exampleof the top heat;

FIG. 5 is a side view showing the shape and structure of a fourthexample of the top heat;

FIG. 6 is a vertical cross-sectional view showing the shape andstructure of a fifth example of the top heat;

FIG. 7a-7c are vertical cross-sectional veiws showing the shape andstructure of a sixth example of the top heat, wherein (a) shows a heaterdisposed on the internal peripheral surface of the lower end portion ofthe rectifying cylinder, (b) shows a heater disposed on the outerperipheral surface of the lower end portion of the rectifying cylinder,(c) shows two heaters disposed respectively on the outer peripheralsurface and the internal peripheral surface of the lower end portion ofthe rectifying cylinder;

FIG. 8 is a chart showing the profile of oxygen density along thelongitudinal axis of the single-crystal silicon;

FIG. 9 is a schematic vertical cross-sectional view of the secondembodiment of the apparatus for manufacturing single crystal siliconaccording to this invention;

FIG. 10 is a schematic vertical cross-sectional view of the thirdembodiment of the apparatus for manufacturing single-crystal siliconaccording to this invention;

FIG. 11 is a diagram showing the controlled circumstances of electriccurrent inputted into the coil to generate a cusp magnetic field;

FIG. 12 is a chart showing the profile of oxygen density along thelongitudinal axis of the single-crystal silicon when a magnetic field isapplied thereon;

FIG. 13 is a schematic vertical cross-sectional view of the fourthembodiment of experimental apparatus for manufacturing single-crystalsilicon according to the method of this invention; and

FIG. 14 is a diagram showing a comparison of the ratios of singlecrystallization from the varions cases.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, embodiments of the method and the apparatus for manufacturingsingle-crystal silicon according to this invention will be explainedwith reference to drawings. FIG. 1 is a schematic verticalcross-sectional view of the first embodiment of the apparatus formanufacturing single-crystal silicon according to this invention. Asshown in FIG. 1, a graphite crucible 3 is installed on the top of acrucible axis 2 which is accommodated within the main chamber 1 in amanner capable of rotating, ascending and descending. The graphitecrucible 3 accommodates a quartz crucible 4 in which melt 5 ofpolycrystalline silicon is stored. A cylindrical main heater 6 and acylindrical adiabatic cylinder 7 are disposed around the graphitecrucible 3. A support member 8 is installed on the top of the adiabaticcylinder 7 and a top heater 9 is fixed on the support member 8.

The pulled up single-crystal silicon 10 is pulled up into a pull chamber11 by way of the openings of the two end portions of the top heater 9.As shown in FIG. 1, Argon used as a carrier gas, which is introducedfrom the upper portion of the pull chamber 11, flows in the direction ofarrows, and passes through the surroundings of the single-crystalsilicon 10 being pulled up, then the carrier gas passes through theclearance between the top heater 9 and the single-crystal silicon 10.After passing through the clearance between the lower end of the topheater 9 and melt 5, the carrier gas is expelled, together with SiO_(x)evaporated from melt 5, to the outside through the bottom of the mainchamber 1.

FIGS. 2 to 7 are illustrations showing the shape and the structure ofvarious top heaters. The top heater 9 shown in FIG. 2 is a one-stagetype, it is shaped like a frustrated cone with two open ends. The topheater 9 is made of carbon CIP, and its upper end is provided with aflange 9a on which the support member 8 of FIG. 1 is hooked. The topheater 9A shown in FIG. 3 is a multiple-stages type, which is made ofcarbon CIP and consists of three piled stages of frustrated top heaters9A1, 9A2 and 9A3. The top heater 9B shown in FIG. 4 is made of carbonCIP and shaped like a hollow cylinder. The top heater 9C shown in FIG. 5is formed by winding a graphite cord into a coil having a frustratedcone shape and coating the cone with SiC. In the above example, thegraphite cord can also be wound into a hollow cylinder. The top heater9D shown in FIG. 6 is a frustrated cone having two open ends, areflection plate 12 covers the surface of a heater 9D1 which is made ofgraphite. The reflection plate 12 is made of carbon CIP, orheat-resisting metals such as molybdenum, tungsten and so on.

FIG. 7 shows a rectifying cylinder made of SiC the lower end of which isprovided with a graphite heater coated with SiC, z wherein (a) shows atop heater 13 having a cylindrical heater 13a disposed on the internalperipheral surface of the lower end portion of the rectifying cylinder14, (b) shows a top heater 15 having a cylindrical heater 15a disposedon the outer peripheral surface of the lower end portion of therectifying cylinder 14, (c) shows a top heater 16 having two cylindricalheaters 16a, 16b respectively disposed on the outer peripheral surfaceand the internal peripheral surface of the lower end portion of therectifying cylinder 14.

FIG. 1 shows an apparatus for manufacturing single-crystal silicon,wherein polycrystalline silicon of 120 kg weight was fed into a 24-inchquartz crucible to pull up an 8-inch single-crystal silicon. In FIG. 1,a top heater as shown in FIG. 2 was used, and it was arranged that anelectrical power of 100 KW is inputted into the main heater and anelectrical power of 15 KW is inputted into the top heater. Forcomparison, in conventional cases such as the manufacturing processdisclosed in the Japanese publication gazette TOKU KAI HEI 2-217388, anelectrical power of 100 KW was inputted into the main heater and anelectrical power of 20 KW was inputted into the bottom heater, andpolycrystalline silicon of 120 kg weight was fed into a 24-inch quartzcrucible to pull up an 8-inch single-crystal silicon.

FIG. 8 is a chart showing the profile of oxygen density along thelongitudinal axis of single-crystal silicon produced under the abovedescribed conditions. In conventional cases, in the zones with lowsolidification ratios such as the portions near the shoulder of singlecrystal ingots, oxygen density was high and decreased following anincrease of the solidification ratio. However, using the manufacturingprocess of this invention, a low oxygen single-crystal ingot with oxygendensity of less than 12×10¹⁷ atoms/cm³ through the whole ingot wasobtained, and the distribution of oxygen density along the longitudinalaxis of the single-crystal ingot also became substantially uniform. Thereasons for the above outcome are that the operation of the top heaterreduced the output of the main heater and no bottom heater was used. Asa result, the heat load on the quartz crucible was reduced and theamount of oxygen dissolved in the melt dropped.

FIG. 9 is a schematic vertical cross-sectional view of the secondembodiment of the apparatus for manufacturing single-crystal siliconaccording to this invention. In this single-crystal siliconmanufacturing apparatus, two coils 17, 17 are provided around the mainchamber 1, the two coils 17, 17 are disposed vertically in such a mannerthat they sandwich the main chamber 1 so as to apply a horizontalmagnetic field to the melt 5. Other structures of FIG. 9 are the same asthose shown in the first embodiment, therefore same numerals attached tosame structural members and explanation are omitted.

FIG. 10 is a schematic vertical cross-sectional view of the thirdembodiment of the apparatus for manufacturing single-crystal siliconaccording to this invention. In this single-crystal siliconmanufacturing apparatus, a ring-shaped upper coil 18 and a ring-shapedlower coil 19 are provided around the main chamber 1 so as to apply acusp magnetic field to the melt 5. Other structures of FIG. 10 are thesame as those shown in the first embodiment, therefore the same numeralsand labels attached to the same structural members are omitted.

In the single-crystal silicon manufacturing apparatus s of the secondand third embodiments shown respectively in FIGS. 9 and 10,polycrystalline silicon of 120 kg weight was fed into a 24-inch quartzcrucible to pull up an 8-inch single crystal silicon. The top heatershown in FIG. 2 was used, and an electrical power of 100 KW was inputtedinto the main heater and an electrical power of 15 KW was inputted intothe top heater. In the second embodiment, the strength of the horizontalmagnetic field was maintained at 4000 gauss, and in the thirdembodiment, the electric current inputted into the coils was controlledbased on the graph shown in FIG. 11 to match the rise of thesolidification ratio.

For comparison, in conventional cases such as the manufacturing processdisclosed in the Japanese publication gazette TOKU KAI HEI 2-229786, anelectrical power of 100 KW was inputted into the main heater, anelectrical power of 20 KW was inputted into the bottom heater, ahorizontal magnetic field of 4000 gauss in strength was applied, andpolycrystalline silicon of 120 kg weight was fed into a 24-inch quartzcrucible to pull up an 8-inch single-crystal silicon.

FIG. 12 is a chart showing the profile of oxygen density along thelongitudinal axis of single-crystal silicon produced under abovedescribed conditions. In FIG. 12, this invention A denotes the result ofthe second embodiment and this invention B denotes the result of thethird embodiment. When using the conventional art, in the zones with lowsolidification ratios such as the portions near the shoulder ofsingle-crystal ingots, the oxygen density was high and decreasedfollowing an increase of the solidification ratio. However, using themanufacturing process of this invention, an extremely low-oxygensingle-crystal ingot with an oxygen density of less than 10×10¹⁷atoms/cm³ through out the whole ingot was obtained, and the distributionof oxygen density along the longitudinal axis of the single-crystalingot also became substantially uniform.

The fourth embodiment of single-crystal silicon manufacturing methodsaccording to this invention is related to not only melting the firststage material fed into the quartz crucible but also an improvement tothe recharging operation when polycrystalline silicon lumps must be fedand melted within the quartz crucible in addition to a preset amount ofremaining melt of the first stage material, or applying a supplementarycharging operation when the first stage material has been melted andadditional material is required to increase the amount of melt.

In the experiments concerning melting of the first stage material, theexperimental apparatus shown in FIG. 13 was used and polycrystallinesilicon of 210 kg weight was fed into a 28-inch quartz crucible to pullup a 12-inch single crystal silicon. On that occasion, a main heater 6and a top heater as shown in FIG. 7(a) were used. For comparison, twoconventional cases, in other words, cases where only the main heater 6and the main heater 6 combined with the bottom heater 20, were utilizedto pull up single-crystal silicon. The amount of electrical powerinputted into each heater is shown in Table one.

                  TABLE ONE                                                       ______________________________________                                        Electrical power inputted into the heaters (KW)                                                    B         C                                                A Conventional Conventional                                                   The invention case-1 case-2                                                        Main      Top     Main heater                                                                           Main    Bottom                                 Process heater heater only heater heater                                    ______________________________________                                        Melting                                                                              170       45      210     170     45                                     material                                                                      Forming                                                                       the body 110 25 150 110 35                                                    of the                                                                        ingot                                                                       ______________________________________                                    

The ratios of single crystallization obtained from the above experimentsare shown in FIG. 14, wherein A denotes the single crystallization ratioobtained by the manufacturing process of this invention, B and C denotethe single crystallization ratios obtained by conventional case-1 (onlythe main heater 6 was used), and conventional case-2 (the main heater 6and the bottom heater 20 were used), respectively. In conventionalcases, only the main heater is used or the main heater and the bottomheater are used, therefore, following the enlargement of the sizes ofsingle-crystal silicon ingots and the increasing of volumes of thequartz crucibles, the heat loads on the quartz crucibles grow. Thisaccelerates, the deterioration of the quartz crucibles. Furthermore,fragments of Sio₂ segregated from the surface of the quartz crucible arecaptured into single-crystal silicon and subsequently polycrystallize,hence, in the case of B, the single crystallization ratio dropped to avalue of 43%, in the case of C, single crystallization ratio dropped toa value of 57%. However, compared with conventional cases, the heat loadin this invention on the quartz crucible was extremely low, consequentlyit was difficult to polycrystallize, and the single crystallizationratio was 80%.

Next, in the experiments concerning recharging material, an apparatuswith the same structure as shown in FIG. 13 was used, andpolycrystalline silicon of 120 kg weight was fed into a 24-inch quartzcrucible to pull up an 8-inch single crystal silicon of 70 kg weight,then polycrystalline silicon rod of substantially 70 kg kg weight wasfurther fed into the 24-inch quartz crucible and was heated. The addedmaterial as above was heated into melt so that a level of the meltsurface is as a predetermined level after being recharged and a secondsingle-crystal silicon was pulled up from the recharged melt. On thisoccasion, the main heater 6 and the top heater 13 were used.

For comparison, two conventional cases, only the main heater 6 and themain heater 6 combined with the bottom heater 20, were utilized to meltmaterial. The electrical power inputted into each heater during themelting of recharged material is shown in Table two.

                  TABLE TWO                                                       ______________________________________                                        Electrical power inputted into the heaters (KW)                                                    Conventional                                                                            Conventional                                     The invention case-1 case-2                                                        Main      Top     Main heater                                                                           Main    Bottom                                 Process heater heater only heater heater                                    ______________________________________                                        Melting                                                                              125       45      170     125     45                                     material                                                                    ______________________________________                                    

In the experiments according to this invention, two single-crystalsilicon ingots were obtained. When utilizing the conventional art, thedeterioration of the quartz crucible was extraordinary, and twosingle-crystal silicon ingots were polycrystallized during the processof pulling up.

As described above, in the process of manufacturing single-crystalsilicon using the CZ method or MCZ method according to this invention, atop heater is provided above the quartz crucible and the outputs of themain heater and the top heater are controlled to pull up single-crystalsilicon. The heat load on the quartz crucible in the process of thisinvention is less than that in the processes of conventional cases inwhich only main heaters or main heaters in combination with bottomheaters are used. By this, the amount of oxygen dissolved in the melt isreduced, and single crystals with low oxygen density or extremely lowoxygen density can be obtained. In addition, the deterioration of thequartz crucible can be slowed down, consequently the singlecrystallization is thus enhanced.

The method and apparatus for manufacturing single crystals according tothis invention can give the best effect to large-diameter single-crystalsilicon ingots, especially those with diameters larger than 12 inches.

What is claimed is:
 1. An apparatus for manufacturing sinzle-crystalsilicon by a Czochralski (CZ) technique, comprising:a quartz cruciblebeing filled with polycrystalline silicon as a raw material; a mainheater for melting a raw material into melt and heating the melt,surrounding the quartz crucible: a top heater disposed above the quartzcrucible; and a pulling up means for pulling up a single crystal siliconfrom the melt, wherein the top heater is provided with at lease one ofthe following functions:(a) rectifying carrier gases; (b) heating thematerial fed into the quartz crucible and the melt; (c) heating thesingle-crystal silicon being pulled up; (d) reducing an amount of oxygendissolved into the melt from the quartz crucible and the deteriorationof the quartz crucible induced by heat load; and (e) giving thermalhistory to the single-crystal silicon pulled up from the melt whereinthe top heater is a truncated cone opened at its two ends or a heaterprovided with one- or multiple-stage cylinders.
 2. The apparatus formanufacturing single-crystal silicon as claimed in claim 1, wherein atleast the surfaces of the top heater, facing the melt are covered byreflection plates.
 3. An apparatus for manufacturing single-crystalsilicon by a CZ technique, comprisinga quartz crucible being filled withpolycrystalline silicon as a raw material; a main heater for melting araw material into melt and heating the melt, surrounding the quartzcrucible; a top heater disposed above the quartz crucible; and a pullingup means for pulling up a single crystal silicon from the melt, whereinthe top heater is provided with at lease one of the followingfunctions:(a) rectifying carrier gases; (b) heating the material fedinto the quartz crucible and the melt; (c) heatino the single-crystalsilicon being pulled up; (d) reducing an amount of oxygen dissolved intothe melt from the quartz crucible and the deterioration of the quartzcrucible induced by heat load; and (e) giving thermal history to thesingle-crystal silicon pulled up from the melt wherein the top heater isdisposed adjacent to the lower end of the cylindrical orreverse-frustrated con-shaped rectifying cylinder.
 4. An apparatus formanufacturing single-crystal silicon by a CZ technique, comprising:aquartz crucible being filled with polycrystalline silicon as a rawmaterial; a main heater for melting a raw material into melt and heatingthe melt, surrounding the quartz crucible; a top heater disposed abovethe quartz crucible; and a plulling up means for pulling up a singlecrystal silicon from the melt, wherein the top heater is provided withat lease one of the following functions:(a) rectifying carrier gases;(b) heating the material fed into the quartz crucible and the melt; (c)heating the single-crystal silicon being pulled up; (d) reducing anamount of oxygen dissolved into the melt from the quartz crucible andthe deterioration of the quartz crucible induced by heat load; and (e)giving thermal history to the single-crystal silicon pulled up from themelt wherein a means for applying a horizontal magnetic field,comprising two coils disposed vertically sandwich the main heater, isprovided.
 5. An apparatus for manufacturing single-crystal silicon by aCZ technique, comprising:a quartz crucible being filled withpolycrystalline silicon as a raw material; a main heater for melting araw material into melt and heating the melt, surrounding the quartzcrucible; a top heater disposed above the quartz crucible; and a pullingup means for pulling up a single crystal silicon from the melt, whereinthe top heater is provided with at lease one of the followingfunctions:(a) rectifying carrier gases; (b) heating the material fedinto the quartz crucible and the melt; (c) heating the single-crystalsilicon being pulled up; (d) reducing an amount of oxygen dissolved intothe melt from the quartz crucible and the deterioration of the quartzcrucible induced by heat load; and (e) giving thermal history to thesingle-crystal silicon pulled up from the melt, wherein a means forapplying a cusp magnetic field, comprising a ring-shaped upper coil anda ring-shaped lower coil disposed around the main heater, is provided.